1. Unit 7: Stoichiometry – Part I
The Mole
Unit 7: Stoichiometry – Part I

2. Lesson Essential Questions
What is a mole?
What is a mole used for?

3. Atoms are really, really small……
We can not work with individual atoms or AMU’s in the lab.
Atomic Mass Unit
WHY?
Because we can’t see things that small!

4. We as scientists work with portions of matter large enough for us to SEE and MASS on a balance using units of……
gramS

5. This presents a problem…..
So how would we keep track of that many atoms?
A pile of atoms large enough for us to see contains billions of atoms.
Copper (II) Sulfate

6. Chemists came up with a new unit.
The MOLE

7. Equivalents or Conversion Factors
1 dozen eggs = 12 eggs
1 ream of paper = 500 pieces of paper
1 rooster = two legs

8. Equivalents or Conversion Factors
1 mole = 6.02 x 1023
There are EXACTLY 12 grams of Carbon-12 in 1 mole of Carbon-12.

9. I did not discover the number. It was just named after me.
Avogadro’s Number
6.02 x 1023
He studied gases and discovered that no matter what the gas, there were the same number of molecules present.
Named in honor of
Amadeo Avogadro.

10. Units for Avogadro’s Number
For instance:
1 mole of pennies =
6.02 x 1023 pennies.
1 mole = 6.02 x 1023 (many different units)
This amount is equivalent to 7 stacks of pennies from the Earth to the moon.

11. Units for Avogadro’s Number
Remember: HOFBrINCl
1 mole Mg= x atoms.
1 mole NaCl= x molecules.
1 mole Cl2 = x molecules.
1 mole SO4-2 = x ions.

12. Calculating Formula Mass
Calculate the formula mass of NaCl. 6 Na 17 Cl
35.453
22.99 g g = g
Therefore, 1 mole of NaCl (6.02 x 1023 molecules) has a mass of g

13. Calculating Formula Mass
Calculate the formula mass of K2O. 19 K 6 O
2(39.10) g g = g
Therefore, 1 mole of K2O (6.02 x 1023 molecules) has a mass of g

14. Calculating Formula Mass
Calculate the formula mass of (NH4)2SO4. 7 N 1 H 16 S
32.066 6 O
2(14.01) g + 8(1.01) g + (32.01) + 4(16.00) g = g
Therefore, 1 mole of (NH4)2SO4 (6.02 x 1023 molecules) has a mass of g

15. Calculating Formula Mass.
Calculate the formula mass of CuSO4 5 H2O.
This type of formula is called a hydrate. It is a salt with water physically attached to it. 29 Cu
63.546 16 S
32.066 6 O 1 H
Example: A salt container with rice intermixed.
Since the water is physically attached how could it be removed?
Therefore, 1 mole of CuSO4 5 H2O (6.02 x 1023 molecules) has
a mass of g .
63.55 g g + 4(16.00) g + 5[2(1.01)+16.00] = g
By heating. When the water is removed the remaining salt is called anhydrous.